Magnetic pick-trp device



June 2, y1931f v H, EMERSON 1,807,654

MAGNETIC PICK-UP DEVICE Original Filed May 6. 1929 Patented June 2, 1931` UNETED STATES .gp-,Maar OFFice? vrcron n.

EMERSON, OE NEW YORK, N. Y., AssreNoE 'ro EENLSEN CORPORATION, or

NEW YORK, N. Y., A CORPORATION or DELAWARE y MAGNETIC Prox-Ur DEVICE Application filed May 6, 1929, Serial NO.' 363,935. Renewed October 11, 1930..4

This invention relates to magnetic pick-up devices for phonographs and has for an obn ject to provide a device of this kind in which the magnetic field is adjustable with relation to the stylus operating member whereby the device is adjustable for recording or reproducing sounds of different intensities or corresponding electrical impulses; another object of the invention is to provide a pair of magnet coils in the magnetic field in operative relation to a vibrating armature. Other objects of the invention will appear from the following specification and the accompanying drawings, in which, Fig. 1 is a side eleva-tion of a magnetic pick-up head constructed according to my invention, Fig. 2 is a side elevation corresponding to Fig. 1, Fig. 3 is an end view of Fig. 1.

A magnetic piclcup device is a device which takes the place of the sound box and diaphragm in the ordinary phonograph and has a stylus engaging the sound groove of the record. This stylus is pivotally mounted and has an armature operatively attached thereto which is vibrated in response to 1novements of the stylus. This armature is mounted in a magnetic field including magnetic coils with the result that vibrating the armature induces a current in the magnet coils which current corresponds to the sound grooves on the record. This arrangement is reversible with the result that by connecting the magnet coils in a circuit controlled by a sound producing device the stylus may be used to inscribe a corresponding groove on the record which is known as recording.

The present invention relates to a device that may be used for recording or reproducing and embodies a novel method of adjusting the magnetic field with relation to the pivotal support of the armature so that the leverage of the magnetic effect operating the armature may be changed to suit a childs voice or the voice of an adult.l The armature is mounted on a self centering support and maintained under constant tension.

In the drawings, 11 is a die cast frame provided with a socket 12 for securing to a supporting arm, (not shown). The frame is provided with a pair of gibs 13 on each side toreceivethe legs 111: ofthe horse-shoeinagnet which creates the magnetic field, Thel coils 15 and 16 are secured to the poles ofthe mag-- net as shown and the magnet slides on the frame 11A to the extent permittedby the 'magnet lcoils in space c. The position of the magnet polesv is adjusted byV the screw 17 Y on the stent 1S worlring'a'gainst'the coil spring 19 whichpro.` vides a micrometer adjustment between theVv poles and the frame.

The frame ends are connected by thefcrossf bar 21 which supports the pivot points` 22 upon Whichthe armature platef23 rests. This plate carries the chucksuppvorting tliefv stylus 211 engaging the record 25 and is rigidly connected with the armature 26which projects throughan aperture in21 and terminates-in the fiat spring 28. This flat spring projects through an aperture in the. framexat 29Vandv is supported by the stifl'f spring 27. which applies a constant tension to- 26 and automatically adjusts itself to any variations inthe` length. of 26, or variations in the position of thepivots 22. i

ByV thisconstruction vthe armature 26 is centered by the spring 27 and by the guides 29 but has a limited free movement, due to the spring support at 28 and the pivotal support at 22, between the poles of magnets 15 and 16.

It is apparent that the closer the poles of the magnets 15 and 16 are to the fixed pivots 22 a greater magnetic eEort will be required to effect the movement of the stylus and, on the other hand, the further these poles are removed from the pivots 22, the magnetic effort will be accordingly lessened by reason of the increased leverage exerted by the poles on the armature. The position of the poles 15 and 16,'is readily adjusted by 17 without in any way affecting the armature, or its mounting.

This adjustment is made by changing the position of the magnetic field relative to the pivotal support of the armature and without in any way affecting Vthe operating circuits.

Having thus described my invention, I claim:

1. In a magnetic pick-up device for phono graph records, the combination, a frame with means for securing to a supporting arm, an armature pivotally mounted on said frame, a stylus secured to said armature engaging the phonograph record, a magnet having poles between which said armature vibrates and means for adjusting the position of said poles relative to the pivotal support of said armature.

2. In a magnetic pick-up device for phonograph records, the combination, a frame with means for securing to a supporting arm, an armature pivotally mounted on said frame, a stylus secured to said armature engaging the phonograph record, a magnet having poles between which said armature vibrates, means for slidably mounting said magnet on said frame and means for adjusting the position of said magnet on said frame.

3. In a magnetic pick-up device for phonograph records, the combination, a frame, an armature pivotally mounted in said frame, a spring for maintaining said armature under tension, a stylus secured to said armature engaging the phonograph record, a magnet having poles between which said armature moves and means for slidably mounting said magnet on said frame whereby the position of said poles relative to the pivotal support of said armature may be varied.

4. In a magnetic pick-up device for phonograph records7 the combination, a frame, an armature pivotally mounted in said frame and a stylus secured to said armature and engaging the phonograph record, a horseshoe magnet slidably mounted on said frame and, a magnet coil secured to each pole of said magnet, said armature mounted to vibrate between said coils.

In testimony whereof I affix my signature.

VICTOR I-I. EMERSON. 

